The present invention relates to a photographic copying apparatus in which a plane of an original and a plane of a copying material, e.g. paper, are arranged at a stable distance from each other.
The photographic copying apparatus of the type under consideration includes an objective with two objective members, which are adjustable for the adjustment of a variable image scale in the copying apparatus, and step motors operative for the adjustment of the positions of those members of the objective.
The German published application No. 29 17 176 discloses a reproduction objective in which a computer calculates the reference-position values of the objective, corresponding to the image scale, and in which the optical element has the coefficients stored in the storage of the computer. With one-time application of the stored coefficients into the computer corrective values of the objective must be taken into consideration.
With the known reproduction objective the reference-positions of the individual objective structural groups are polynominals in which the various cofficients are to be multiplied by the exponents of the image scale. This construction has, however, comparatively small storage capacity but is rather expensive. Furthermore, correction possibilities in this known apparatus are quite limited.